This number takes account of VAT and inflation, but is still below an £80 billion forecast by the Institute for Economic Affairs, a respected free market think tank. The Institute of Directors, which represents more than 35,000 businesses, will identify road and rail projects that would be more valuable to the economy than HS2.

The institute is also expected to publish a survey showing more than half of its members think the project does not represent a good use of public money.

The British Chambers of Commerce, which represents 92,000 firms, has strongly supported HS2. However, John Longworth, the group’s director general, said that he would not back the rail link “at any cost”. “If the facts change significantly I would take another look at it,” Mr Longworth said.